A plant of the above-mentioned type is described in Swedish patent specification 8700960-1 (456 757; corresponding to EP 881012041 (0 285 825) and U.S. Pat. No. 4,860,535). In such a plant the plant is started by the generator therein being switched to a motor, which accelerates the gas turbine of the plant to full, synchronous speed. This requires energy from the network, and limits the applicability to relatively small plants, for example with a gas turbine power of 15-17 MW.
Starting equipment for a larger plant of the above-mentioned type would become very extensive, both from the points of view of design and economy, and it is desired not to take out such great power for starting as would be required from the network in case of generator-motor start.